The urinary tract is susceptible to the obstruction of urine flow either by endogenous causes such as the formation of stones, external compression by anatomic abnormalities, or neoplastic growth. Obstruction can also be iatrogenic, induced by manipulation or surgery. Ureteral stents have been developed to bypass such urinary tract obstructions. Typically, ureteral stents are made of biocompatible plastic materials. During a typical surgical procedure to bypass a urinary tract obstruction, the ureteral stent is passed over a guide wire. The stent is tubular to allow for the flow of urine, just large enough to fit over a guide wire, but of several diameters within a small range (2-3 mm) and with “S” shaped ends which act as anchors that prevent the stent's migration. The ureteral stents are often placed at the end of an operation or by themselves, when no other procedure is indicated, but the relief of the obstruction.
Typically, ureteral stents are introduced through the urethra via a fiberoptic endoscopic instrument, such as for example, a cystoscope. The set-up for an endoscopic procedure typically includes light and water sources, and local anesthesia or sedation. Stent removal is also typically performed using fiberoptic endoscopic instruments. Fiberoptic endoscopic instruments are generally guided through a urethra visually, with a doctor manually guiding the endoscope based on the images observed through the fiberscope. The endoscopic instrument is typically guided to the stent at which point it is removed with a “foreign body” grasper.
Visually guiding endoscopes through the urinary tract in this manner is often labor intensive, and requires special set-up and assistant time. Moreover, some endoscopes are large enough to allow for the passage foreign body graspers, causing discomfort for patients. Fluid flow and local anesthetics are also frequently used during removal procedures, however discomfort is not completely eliminated. Attempts have been made to remove stents without relying on visual instruments such as a cystoscope by attaching a string to the stent. However, the strings tend to retract and reside within the urethra still requiring the use of a cystoscope for their retrieval.
Other drawbacks exist.